The present invention relates to a blanket used in offset printing on metal sheets and plastic films.
Conventionally, a blanket for offset printing is formed of a flexible material, whose front surface is formed with a synthetic rubber layer. Since the synthetic rubber layer, or front surface, is in the state of receiving ink during printing process, the vehicle and the like contained in the ink permeate the rubber layer, tending to soften the surface. This phenomenon increases the ability of the blanket surface to carry ink, so that too much ink is transferred to a plastic film, metal sheet or other material to be printed, requiring an increased force of separating the printed material from the blanket surface. Such increase in the separating force does not matter if the printed material is paper, but if the printed material is a metal sheet or plastic film, said increase causes the printed material to greatly curl on the printed-material discharging side, making it impossible to achieve a high printing speed of, e.g., 3,000 sheets per hour or above.